Android isn't exactly known for having top-notch security, especially since you can sideload just about anything you want and the older versions of the OS don't get significant updates. Back in June we heard about a nasty virus that had been affecting some older Fire TV devices, and now Amazon's rolling out an update to keep them more secure.
That worm specifically affected devices where people had been fiddling with the developer options and allowed ADB debugging. That was usually done by people who had been sideloading apps, and once it had been done once all future ADB connections were allowed by default. Once in the virus began throttling the hardware, mining cryptocurrency, and then attempting to spread to other vulnerable devices on the same network.
The good news is that the latest software update hitting Fire TV devices (18.104.22.168) is going to make things more secure - regardless of what developer settings you've been playing around with. More specifically it prompts users to accept ADB connections each time, so something nasty can't sneak in and get to work without being noticed.
So if you have a Fire device, make sure you get that latest update installed when it's available. If you get a prompt for the connection you don't recognise, make sure to deny it. It won't be anything good. [AFTVNews via Engadget]